1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a wireless communication technology, and in particular, to a structure of a transmission packet for a link adaptation mechanism that can efficiently transmits/receives uncompressed data using a link adaptation mechanism in a high-frequency wireless communication, and a transmitting/receiving device and method using the same.
2. Description of the Related Art
With the progress of a wireless network, there has been an increasing demand for the transmission of mass multimedia data and studies for an effective transmission method in a wireless network environment. In addition, a necessity for wireless transmission of a high-quality video, such as a DVD (Digital Video Disk) video, an HDTV (High Definition Television) video, or the like, among various home devices tends to increase.
At present, a task group of IEEE 802.15.3c is considering a technical standard for transmitting mass data in a wireless home network. This standard, called mmWave (Millimeter Wave), uses an electrical wave having a physical wavelength of several millimeters for the sake of the transmission of the mass data (that is, an electrical wave having a frequency 30 GHz to 300 GHz). In the related art, this frequency band is an unlicensed band and is limitedly used, for example, communication carriers, radio astronomy, or vehicle anti-collision.
FIG. 1 is a diagram showing the comparison result of a frequency band between the standard base on IEEE 802.11 and the millimeter wave (mmWave). In IEEE 802.11b or IEEE 802.11g, a carrier frequency is 2.4 GHz, and a channel bandwidth is about 20 MHz. Further, in IEEE 802.11a or IEEE 802.11n, a carrier frequency is 5 GHz, and a channel bandwidth is about 20 MHz. In contrast, in the mmWave, a carrier frequency of 60 GHz is used, and a channel bandwidth is about 0.5 to 2.5 GHz. Accordingly, it can be seen that the mmWave uses much larger carrier frequency and channel bandwidth than the existing standard based on IEEE 802.11. As such, if a high-frequency signal having a wavelength in millimeters (Millimeter Wave) is used, a high transmission rate of several Gbps can be obtained, and the size of an antenna can be set to be not more than 1.5 mm. Then, a single chip including the antenna can be implemented. In addition, an attenuation ratio in air is very high, and thus interference between the apparatuses can be reduced.
In recent years, the transmission of uncompressed audio or video data (hereinafter, referred to as uncompressed data) between wireless apparatuses using a high bandwidth of the millimeter wave has been studied. Compressed AV data is compressed with a partial loss through processes, such as motion compensation, DCT conversion, quantization, variable length coding, and the like, such that portions insensitive to the sense of sight or the sense of hearing is eliminated. In contrast, uncompressed data includes digital values (for example, R, G, and B components) representing pixel components as they are.
Accordingly, while bits in the compressed AV data have similar importance, bits in the uncompressed data have different importance. For example, as shown in FIG. 2, in case of an 8-bit video, one pixel component is expressed by 8 bits. Among these, a bit that expresses the highest order (the highest bit) is a most significant bit (MSB), and a bit that expresses the lowest order (the lowest bit) is a least significant bit (LSB). That is, the bits in one byte data having 8 bits have different importance in restoring a video signal or an audio signal. If an error occurs in a bit having high importance during transmission, the error can be easily detected, compared with a case where an error occurs in a bit having lower importance. Accordingly, bits having high importance need to be protected such that an error does not occur in wireless transmission, compared with bits having lower importance. However, in a known transmission system based on IEEE 802.11, an error correction system and a retransmission system at the same coding rate are used for all bits to be transmitted.
FIG. 3 is a diagram showing the structure a physical layer transmission frame (PHY Protocol Data Unit; PPDU) based on IEEE 802.11a. A PPDU 30 includes a preamble, a signal field, and a data field. The preamble is a signal for synchronization of the PHY hierarchy and channel estimation. The preamble has a plurality of short training signals and long training signals. The signal field includes a RATE field representing a transmission rate, a LENGTH field representing the length of the PPDU, and the like. Typically, the signal field is coded by one symbol. The data field has a PSDU, a tail bit, and a pad bit. Data to be actually transmitted is included in the PSDU.
Meanwhile, between a transmitting device transmitting the uncompressed data and a receiving device receiving the uncompressed data, there exists a link adaptation mechanism that copes with a state of a channel changing every moment. The link adaptation process is performed by adjusting parameters, such as the transmission rate, the size of the transmission frame, and the power of the transmitting/receiving device. However, in the link adaptation mechanism, there is a limit for a bandwidth resource due to the use of a management frame, which causes deterioration of efficiency in data transmission.